Aurigae54 t1_iydggw9 wrote on November 30, 2022 at 4:14 PM

Reply to comment by ialsoagree in ELI5: Why does stuff dissolve in hot water more? by samuelma

Thats not true. Hydrogen bonding is an intermolecular force of attraction, as in between two molecules, and it certainly doesn't only apply to ionic substances being dissolved. The reason why water is a liquid at room temperature is because of hydrogen bonding between the positive hydrogen ends of one water molecule being attracted to the negative end of a second water molecule.

I think the point you were getting at was intramolecular vs intermolecular forces of attraction, and that in general intramolecular forces are considered to be true bonds, as they hold the atoms in different molecules and compounds together whereas intermolecular forces, not being nearly as strong as intra, are generally demoted to just being weak attractive forces, with hydrogen bonding being confusingly named as its not even a true bond by these metrics. This whole thread seems pretty semantic, 'bond' is just a strong word to describe an attractive force, at the end of the day and at its core a triple covalent bond is not that different from dispersion forces, they are just two ends of a spectrum representing how little/how much energy you need to break an attraction.

ialsoagree t1_iydj3qr wrote on November 30, 2022 at 4:31 PM

You said "that's not true" but then discussed a bunch of stuff I never mentioned. I never mentioned whether or not hydrogen bonding only applies to dissolving substances. I never mentioned water being a liquid at room temperature.

But I will address this:

>they are just two ends of a spectrum representing how little/how much energy you need to break an attraction.

At a physical level I agree with you. But not at a categorical level. These things are categorically distinct when we talk about them because of the size of disparity in energy required.

Let a cup of salt water sit and salt will spontaneously crystallize out of the water within hours. Just through Brownian motion.

Stable molecules could take billions of years to change their structure, or longer. This is why we categorize "water" as it's own molecule, and "salt" as it's own molecule, but we don't categorize "salt water" as a molecule - we categorize it as a solution of 2 molecules.